Abstract: The invention is directed to a method and an arrangement for harmonic wave suppression in AC voltage-operated PTC heaters in which a harmonic component which is generated in the current of the PTC heater and which contains predominantly the third harmonic of the heating current is compensated by the superposition of correction signals. It is the object of the invention to find a novel possibility for a simple and robust suppression of harmonic waves in AC voltage-operated PTC heaters in which the permissible limiting values for harmonic distortion are not exceeded as a result of changes in heating output. This object is met according to the invention in that a voltage modulation is generated in a voltage modulator (4) arranged in series with the PTC heater (3), wherein a defined partial amplitude attenuation of the sinusoidal supply voltage (U1) is carried out as voltage modulation for suppressing the third harmonic in the heating current (I2) of the PTC heater (3).